Biodegradable polylactide nonwovens with improved fluid management properties

ABSTRACT

A biodegradable nonwoven material having improved fluid management properties. The nonwoven material may be produced using thermoplastic compositions which comprise an unreacted mixture of a poly(lactic acid) polymer; a polybutylene succinate polymer or a polybutylene succinate adipate polymer, or a mixture of such polymers; and a wetting agent. The thermoplastic composition exhibits substantial biodegradable properties yet is easily processed. The biodegradable nonwoven materials may be used in a disposable absorbent product intended for the absorption of fluids such as body fluids.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part patent application of U.S.patent application Ser. No. 09/222,094, filed on Dec. 29, 1998 now U.S.Pat. No. 6,211,294, which is a divisional patent application of U.S.patent application Ser. No. 08/962,432, filed on Oct. 31, 1997, now U.S.Pat. No. 5,910,545, issued Jun. 8, 1999.

FIELD OF THE INVENTION

The present invention relates to a biodegradable nonwoven materialhaving improved fluid management properties. The nonwoven material maybe produced from polymer blends. These blends may include multicomponentfibers. These multicomponent fibers comprise an unreacted mixture of apoly(lactic acid) polymer, a polybutylene succinate polymer or apolybutylene succinate adipate polymer or a mixture of such polymers,and a wetting agent. The multicomponent fiber exhibits substantialbiodegradable properties yet is easily processed. The biodegradablenonwoven materials may be used in a disposable absorbent productintended for the absorption of fluids, such as body fluids.

BACKGROUND OF THE INVENTION

Disposable absorbent products currently find widespread use in manyapplications. For example, in the infant and child care areas, diapersand training pants have generally replaced reusable cloth absorbentarticles. Other typical disposable absorbent products include femininecare products such as sanitary napkins or tampons, adult incontinenceproducts, and health care products such as surgical drapes or wounddressings. A typical disposable absorbent product generally comprises acomposite structure including a topsheet, a backsheet, and an absorbentstructure between the topsheet and backsheet. These products usuallyinclude some type of fastening system for fitting the product onto thewearer.

Disposable absorbent products are typically subjected to one or moreliquid insults, such as of water, urine, menses, or blood, during use.As such, the outer cover backsheet materials of the disposable absorbentproducts are typically made of liquid-insoluble and liquid impermeablematerials, such as polypropylene films, that exhibit a sufficientstrength and handling capability so that the disposable absorbentproduct retains its integrity during use by a wearer and does not allowleakage of the liquid insulting the product.

Although current disposable baby diapers and other disposable absorbentproducts have been generally accepted by the public, these productsstill have need of improvement in specific areas. For example, manydisposable absorbent products can be difficult to dispose of. Forexample, attempts to flush many disposable absorbent products down atoilet into a sewage system typically lead to blockage of the toilet orpipes connecting the toilet to the sewage system. In particular, theouter cover materials typically used in the disposable absorbentproducts generally do not disintegrate or disperse when flushed down atoilet so that the disposable absorbent product cannot be disposed of inthis way. If the outer cover materials are made very thin in order toreduce the overall bulk of the disposable absorbent product so as toreduce the likelihood of blockage of a toilet or a sewage pipe, then theouter cover material typically will not exhibit sufficient strength toprevent tearing or ripping as the outer cover material is subjected tothe stresses of normal use by a wearer.

Furthermore, solid waste disposal is becoming an ever increasing concernthroughout the world. As landfills continue to fill up, there has beenan increased demand for material source reduction in disposableproducts, the incorporation of more recyclable and/or degradablecomponents in disposable products, and the design of products that canbe disposed of by means other than by incorporation into solid wastedisposal facilities such as landfills.

As such, there is a need for new materials that may be used indisposable absorbent products that generally retain their integrity andstrength during use, but after such use, the materials may be moreefficiently disposed of. For example, the disposable absorbent productmay be easily and efficiently disposed of by composting. Alternatively,the disposable absorbent product may be easily and efficiently disposedof to a liquid sewage system wherein the disposable absorbent product iscapable of being degraded.

Although degradable monocomponent fibers are known, problems have beenencountered with their use. In particular, known degradable fiberstypically do not have good thermal dimensional stability such that thefibers usually undergo severe heat-shrinkage due to the polymer chainrelaxation during downstream heat treatment processes such as thermalbonding or lamination.

For example, although fibers prepared from poly(lactic acid) polymer areknown, problems have been encountered with their use. In particular,poly(lactic acid) polymers are known to have a relatively slowcrystallization rate as compared to, for example, polyolefin polymers,thereby often resulting in poor processability of the aliphaticpolyester polymers. In addition, the poly(lactic acid) polymersgenerally do not have good thermal dimensional-stability. Thepoly(lactic acid) polymers usually undergo severe heat-shrinkage due tothe relaxation of the polymer chain during downstream heat treatmentprocesses, such as thermal bonding and lamination, unless an extra stepsuch as heat setting is taken. However, such a heat setting stepgenerally limits the use of the fiber in in-situ nonwoven formingprocesses, such as spunbond and meltblown, where heat setting is verydifficult to be accomplished.

Additionally, one of the more important components of many personal carearticles is the body-side liner. The liner is usually comprised of asurfactant-treated polyolefin spunbond. For a spunbond to be implementedas a liner, it is desired that the material be wettable to promoteintake of fluid insults. In addition to rapid intake, it is desired thatthe composite absorbent product keep the user's skin dry. In addition,it is desirable for the spunbond material to feel soft against the skin.The current spunbond diaper liner has a number of problems associatedwith it. First, it is comprised of polyolefinic materials and does notdegrade. Due to the hydrophobic nature of these materials, the linermust be treated with a surfactant to make it wettable. Because there isno permanent anchoring of the surfactant to the polyolefin, it has atendency to wash off during multiple insults, increasing intake times ofthe nonwovens.

Accordingly, there is a need for a nonwoven material useful as awettable structure with improved fluid management properties such asfaster intake times and improved skin dryness. Additionally there is aneed for a nonwoven material that is biodegradable while also providingthese improved fluid management properties.

SUMMARY OF THE INVENTION

It is therefore desired to provide a nonwoven material having improvedfluid management properties.

It is also desired to provide a nonwoven material having faster intaketimes.

It is also desired to provide a nonwoven material having improved skindryness.

It is also desired to provide a nonwoven material that is biodegradablewhile also providing improved fluid management properties.

It is also desired to provide a nonwoven material comprising athermoplastic composition which exhibits desired processability, liquidwettability, and thermal dimensional-stability properties.

It is also desired to provide a nonwoven material comprising athermoplastic composition which may be easily and efficiently formedinto a fiber.

It is also desired to provide a nonwoven material comprising athermoplastic composition which is suitable for use in preparingnonwoven structures.

It is also desired to provide a disposable absorbent product that may beused for the absorption of fluids such as bodily fluids, yet which suchdisposable absorbent product comprises components that are readilydegradable in the environment.

These desires are fulfilled by the present invention which provides anonwoven material comprising a thermoplastic composition that issubstantially biodegradable and yet which is easily prepared and readilyprocessable into desired final nonwoven structures.

One aspect of the present invention concerns a nonwoven material havinga thermoplastic composition that comprises a mixture of a firstcomponent, a second component, and a third component.

One embodiment of such a thermoplastic composition comprises anunreacted mixture of a poly(lactic acid) polymer; a polybutylenesuccinate polymer or a polybutylene succinate adipate polymer or amixture of such polymers; and a wetting agent for the poly(lactic acid)polymer, the polybutylene succinate polymer or the polybutylenesuccinate adipate polymer or a mixture of such polymers.

In another aspect, the present invention concerns a multicomponent fiberthat is substantially degradable and yet which is easily prepared andreadily processable into the desired final nonwoven structures.

One aspect of the present invention concerns a multicomponent fiber thatcomprises an unreacted mixture of a poly(lactic acid) polymer; apolybutylene succinate polymer or a polybutylene succinate adipatepolymer or a mixture of such polymers; and a wetting agent for thealiphatic polyester polymer and the polybutylene succinate polymer orthe polybutylene succinate adipate polymer or a mixture of suchpolymers.

In another aspect, the present invention concerns a nonwoven structurecomprising the multicomponent fiber disclosed herein.

One embodiment of such a nonwoven structure is a frontsheet useful in adisposable absorbent product.

In another aspect, the present invention concerns a process forpreparing the nonwoven material disclosed herein.

In another aspect, the present invention concerns a disposable absorbentproduct comprising the multicomponent fiber disclosed herein.

DETAILED DESCRIPTION OF INVENTION

The present invention is directed to a biodegradable nonwoven materialwhich includes a thermoplastic composition comprising a first component,a second component, and a third component. As used herein, the term“thermoplastic” is meant to refer to a material that softens whenexposed to heat and substantially returns to its original condition whencooled to room temperature.

It has been discovered that, by using an unreacted mixture of apoly(lactic acid) polymer, a polybutylene succinate polymer or apolybutylene succinate adipate polymer or a mixture of such polymers,and a wetting agent, a thermoplastic composition may be prepared whereinsuch thermoplastic composition is substantially degradable yet whichthermoplastic composition is easily processed into fibers and nonwovenstructures that exhibit effective fibrous mechanical properties.

The first component in the thermoplastic composition is poly(lacticacid) polymer. Poly(lactic acid) polymer is generally prepared by thepolymerization of lactic acid. However, it will be recognized by oneskilled in the art that a chemically equivalent material may also beprepared by the polymerization of lactide. As such, as used herein, theterm “poly(lactic acid) polymer” is intended to represent the polymerthat is prepared by either the polymerization of lactic acid or lactide.

Lactic acid and lactide are known to be asymmetrical molecules, havingtwo optical isomers referred to, respectively, as the levorotatory(hereinafter referred to as “L”) enantiomer and the dextrorotatory(hereinafter referred to as “D”) enantiomer. As a result, bypolymerizing a particular enantiomer or by using a mixture of the twoenantiomers, it is possible to prepare different polymers that arechemically similar yet which have different properties. In particular,it has been found that by modifying the stereochemistry of a poly(lacticacid) polymer, it is possible to control, for example, the meltingtemperature, melt rheology, and crystallinity of the polymer. By beingable to control such properties, it is possible to prepare athermoplastic composition and a multicomponent fiber exhibiting desiredmelt strength, mechanical properties, softness, and processabilityproperties so as to be able to make attenuated, heat-set, and crimpedfibers.

Examples of poly(lactic acid) polymers that are suitable for use in thepresent invention include a variety of poly(lactic acid) polymers thatare available from Chronopol Inc., Golden, Colo.

It is generally desired that the poly(lactic acid) polymer be present inthe thermoplastic composition in an amount effective to result in thethermoplastic composition exhibiting desired properties. The poly(lacticacid) polymer will be present in the thermoplastic composition in aweight amount that is greater than 0 but less than 100 weight percent,beneficially between about 5 weight percent to about 95 weight percent,suitably between about 10 weight percent to about 90 weight percent, andmore suitably between about 15 weight percent to about 85 weightpercent, wherein all weight percents are based on the total weightamount of the poly(lactic acid) polymer, the polybutylene succinatepolymer or polybutylene succinate adipate polymer or a mixture of suchpolymers, and the wetting agent present in the thermoplasticcomposition. The compositional ratio of the three components in thethermoplastic composition is generally important to obtain the desiredproperties of the thermoplastic composition, such as wettability,biodegradability, thermal stability and processability.

The second component in the thermoplastic composition is a polybutylenesuccinate polymer, a polybutylene succinate adipate polymer, or amixture of such polymers. A polybutylene succinate polymer is generallyprepared by the condensation polymerization of a glycol and adicarboxylic acid or an acid anhydride thereof. A polybutylene succinatepolymer may either be a linear polymer or a long-chain branched polymer.A long-chain branched polybutylene succinate polymer is generallyprepared by using an additional polyfunctional component selected fromthe group consisting of trifunctional or tetrafunctional polyols,oxycarboxylic acids, and polybasic carboxylic acids. Polybutylenesuccinate polymers are known in the art and are described, for example,in European Patent Application 0 569 153 A2 to Showa Highpolymer Co.,Ltd., Tokyo, Japan. A polybutylene succinate adipate polymer isgenerally prepared by the polymerization of at least one alkyl glycoland more than one aliphatic multifunctional acid. Polybutylene succinateadipate polymers are also known in the art.

Examples of polybutylene succinate polymers and polybutylene succinateadipate polymers that are suitable for use in the present inventioninclude a variety of polybutylene succinate polymers and polybutylenesuccinate adipate polymers that are available from Showa HighpolymerCo., Ltd., Tokyo, Japan, under the designation Bionolle 1903polybutylene succinate polymer, with long chain branches, or Bionolle1020 polybutylene succinate polymer, which is an essentially linearpolymer.

It is generally desired that the polybutylene succinate polymer, thepolybutylene succinate adipate polymer, or a mixture of such polymers bepresent in the thermoplastic composition in an amount effective toresult in the thermoplastic composition exhibiting desired properties.The polybutylene succinate polymer, the polybutylene succinate adipatepolymer, or a mixture of such polymers will be present in thethermoplastic composition in a weight amount that is greater than 0 butless than 100 weight percent, beneficially between about 5 weightpercent to about 95 weight percent, suitably between about 10 weightpercent to about 90 weight percent, and more suitably between about 15weight percent to about 85 weight percent, wherein all weight percentsare based on the total weight amount of the poly(lactic acid) polymer;the polybutylene succinate polymer, the polybutylene succinate adipatepolymer, or a mixture of such polymers; and the wetting agent present inthe thermoplastic composition.

It is generally desired that the poly(lactic acid) polymer and thepolybutylene succinate polymer and/or the polybutylene succinate adipatepolymer exhibit a weight average molecular weight that is effective forthe thermoplastic composition to exhibit desirable melt strength, fibermechanical strength, and fiber spinning properties. In general, if theweight average molecular weight of a particular polymer is too high,this represents that the polymer chains are heavily entangled which mayresult in a thermoplastic composition comprising that polymer beingdifficult to process. Conversely, if the weight average molecular weightof a particular polymer is too low, this represents that the polymerchains are not entangled enough which may result in a thermoplasticcomposition comprising that polymer exhibiting a relatively weak meltstrength, making high speed processing very difficult. Thus, poly(lacticacid) polymers, polybutylene succinate polymers, and/or polybutylenesuccinate adipate polymers suitable for use in the present inventionrespectively exhibit weight average molecular weights that arebeneficially between about 10,000 to about 2,000,000, more beneficiallybetween about 50,000 to about 400,000, and suitably between about100,000 to about 300,000. The weight average molecular weight forpolymers or polymer blends can be determined using a method as describedin the Test Methods section herein.

It is also desired that the poly(lactic acid) polymer and thepolybutylene succinate polymer and/or the polybutylene succinate adipatepolymer exhibit a polydispersity index value that is effective for thethermoplastic composition to exhibit desirable melt strength, fibermechanical strength, and fiber spinning properties. As used herein,“polydispersity index” is meant to represent the value obtained bydividing the weight average molecular weight of a polymer by the numberaverage molecular weight of the polymer. In general, if thepolydispersity index value of a particular polymer is too high, athermoplastic composition comprising that polymer may be difficult toprocess due to inconsistent processing properties caused by polymersegments comprising low molecular weight polymers that have lower meltstrength properties during spinning. Thus, it is desired that thepoly(lactic acid) polymer, the polybutylene succinate polymer, and/orthe polybutylene succinate adipate polymer respectively exhibit apolydispersity index value that is beneficially between about 1 to about15, more beneficially between about 1 to about 4, and suitably betweenabout 1 to about 3. The number average molecular weight for polymers orpolymer blends can be determined using a method as described in the TestMethods section herein.

In the present invention, it is desired that the poly(lactic acid)polymer, the polybutylene succinate polymer, and the polybutylenesuccinate adipate polymer be biodegradable. As a result, the nonwovenstructure having the thermoplastic composition comprising these polymerswill be substantially degradable when disposed of to the environment andexposed to air and/or water. As used herein, “biodegradable” is meant torepresent that a material degrades from the action of naturallyoccurring microorganisms such as bacteria, fungi, and algae.

In the present invention, it is also desired that the poly(lactic acid)polymer, the polybutylene succinate polymer, and the polybutylenesuccinate adipate polymer be compostable. As a result, the nonwovenstructure having the thermoplastic composition comprising these polymerswill be substantially compostable when disposed of to the environmentand exposed to air and/or water. As used herein, “compostable” is meantto represent that the material is capable of undergoing biologicaldecomposition in a compost site such that the material is not visuallydistinguishable and breaks down into carbon dioxide, water, inorganiccompounds, and biomass, at a rate consistent with known compostablematerials.

As used herein, the term “hydrophobic” refers to a material having acontact angle of water in air of at least 90 degrees. In contrast, asused herein, the term “hydrophilic” refers to a material having acontact angle of water in air of less than 90 degrees. For the purposesof this application, contact angle measurements are determined as setforth in the Test Methods section herein. The general subject of contactangles and the measurement thereof is well known in the art as, forexample, in Robert J. Good and Robert J. Stromberg, Ed., in “Surface andColloid Science—Experimental Methods”, Vol. II, (Plenum Press, 1979).

It is generally desired that the poly(lactic acid) polymer, thepolybutylene succinate polymer, the polybutylene succinate adipatepolymer, or a mixture of such polymers, be melt processable. It istherefore desired that the polymers used in the present inventionexhibit a melt flow rate that is beneficially between about 1 gram per10 minutes to about 600 grams per 10 minutes, suitably between about 5grams per 10 minutes to about 200 grams per 10 minutes, and moresuitably between about 10 grams per 10 minutes to about 150 grams per 10minutes. The melt flow rate of a material may be determined according toASTM Test Method D1238-E, incorporated in its entirety herein byreference.

As used herein, the term “fiber” or “fibrous” is meant to refer to amaterial wherein the length to diameter ratio of such material isgreater than about 10. Conversely, a “nonfiber” or “nonfibrous” materialis meant to refer to a material wherein the length to diameter ratio ofsuch material is about 10 or less.

Either separately or when mixed together, the poly(lactic acid) polymerand the polybutylene succinate polymer and/or the polybutylene succinateadipate polymer are generally hydrophobic. Since it is desired that thebiodegradable nonwovens of the present invention prepared from thethermoplastic composition, generally be hydrophilic, it has been foundthat there is a need for the use of another component in thethermoplastic composition of the present invention in order to achievethe desired properties. Furthermore, it has been found desirable toimprove the processability of the poly(lactic acid) polymer, and thepolybutylene succinate polymer and/or the polybutylene succinateadipate, since such polymers are not chemically identical and are,therefore, somewhat incompatible with each other which negativelyaffects the processing of a mixture of such polymers. For example, thepoly(lactic acid) polymer, the polybutylene succinate polymer, and/orthe polybutylene succinate adipate polymer are sometimes difficult toeffectively mix and prepare as an essentially homogeneous mixture ontheir own. As such, the present invention generally requires the use ofa wetting agent that allows for the effective preparation and processingof the poly(lactic acid) polymer, the polybutylene succinate polymer,and/or the polybutylene succinate adipate polymer into a singlethermoplastic composition.

Thus, the third component in the thermoplastic composition is a wettingagent for the poly(lactic acid) polymer and the polybutylene succinatepolymer and/or the polybutylene succinate adipate polymer. Wettingagents suitable for use in the present invention will generally comprisea hydrophilic section which will generally be compatible to poly(lacticacid) polymer and the hydrophilic sections of polybutylene succinatepolymer or polybutylene succinate adipate polymer and a hydrophobicsection which will generally be compatible to the hydrophobic sectionsof polybutylene succinate polymer or polybutylene succinate adipatepolymer. These hydrophilic and hydrophobic sections of the wetting agentwill generally exist in separate blocks so that the overall wettingagent structure may be di-block or random block. It is generally desiredthat the wetting agent initially functions as a plasticizer and an agentto enhance cohesion between the different polymers in order to improvethe preparation and processing of the thermoplastic composition. It isthen generally desired that the wetting agent then serves as asurfactant in the nonwoven material processed from the thermoplasticcomposition by modifying the contact angle of water in air of theprocessed material. The hydrophobic portion of the wetting agent may be,but is not limited to, a polyolefin such as polyethylene orpolypropylene. The hydrophilic portion of the wetting agent may containethylene oxide, ethoxylates, glycols, alcohols or any combinationsthereof. Examples of suitable wetting agents include UNITHOX®480 andUNITHOX®750 ethoxylated alcohols, or UNICID® Acid Amide Ethoxylates, allavailable from Petrolite Corporation of Tulsa, Okla.

It is generally desired that the wetting agent exhibit a weight averagemolecular weight that is effective for the thermoplastic composition toexhibit desirable melt strength, fiber mechanical strength, and fiberspinning properties. In general, if the weight average molecular weightof a wetting agent is too high, the wetting agent will not blend wellwith the other components in the thermoplastic composition because thewetting agent's viscosity will be so high that it lacks the mobilityneeded to blend. Conversely, if the weight average molecular weight ofthe wetting agent is too low, this represents that the wetting agentwill generally not blend well with the other components and have such alow viscosity that it causes processing problems. Thus, wetting agentssuitable for use in the present invention exhibit weight averagemolecular weights that are beneficially between about 1,000 to about100,000, suitably between about 1,000 to about 50,000, and more suitablybetween about 1,000 to about 10,000. The weight average molecular weightfor the poly(lactic acid) can be determined using a method as describedin the Test Methods section herein.

It is generally desired that the wetting agent exhibit an effectivehydrophilic-lipophilic balance ratio (HLB ratio). The HLB ratio of amaterial describes the relative ratio of the hydrophilicity of thematerial. The HLB ratio is calculated as the weight average molecularweight of the hydrophilic portion divided by the total weight averagemolecular weight of the material, which value is then multiplied by 20.If the HLB ratio value is too low, the wetting agent will generally notprovide the desired improvement in hydrophilicity. Conversely, if theHLB ratio value is too high, the wetting agent will not blend into thethermoplastic composition because of chemical incompatibility anddifferences in viscosities with the other components. Thus, wettingagents useful in the present invention exhibit HLB ratio values that arebeneficially between about 10 to about 40, suitably between about 10 toabout 20, and more suitably between about 12 to about 16.

It is generally desired that the wetting agent be present in thethermoplastic composition in an amount effective to result in thethermoplastic composition exhibiting desired properties such asdesirable heat shrinkage and desirable contact angle values. In general,a minimal amount of the wetting agent will be needed to achieve aneffective blending and processing with the other components in thethermoplastic composition. In general, too much of the compatibilizermay lead to processing problems of the thermoplastic composition or to afinal thermoplastic composition that does not exhibit desired propertiessuch as desired Advancing and Receding contact angle values. The wettingagent will be present in the thermoplastic composition in a weightamount that is greater than 0 to about 15 weight percent, beneficiallybetween about 0.5 weight percent to about 15 weight percent, morebeneficially between about 1 weight percent to about 13 weight percent,suitably between about 1 weight percent to about 10 weight percent, andmore suitably between about 1 weight percent to about 5 weight percent,wherein all weight percents are based on the total weight amount of thepoly(lactic acid) polymer; the polybutylene succinate polymer, thepolybutylene succinate adipate polymer, or a mixture of such polymers;and the wetting agent present in the thermoplastic composition.

While the principal components of the thermoplastic composition used inthe present invention have been described in the foregoing, suchthermoplastic composition is not limited thereto and can include othercomponents not adversely effecting the desired properties of thethermoplastic composition. Exemplary materials which could be used asadditional components would include, without limitation, pigments,antioxidants, stabilizers, surfactants, waxes, flow promoters, solidsolvents, plasticizers, nucleating agents, particulates, and othermaterials added to enhance the processability of the thermoplasticcomposition. If such additional components are included in athermoplastic composition, it is generally desired that such additionalcomponents be used in an amount that is beneficially less than about 10weight percent, more beneficially less than about 5 weight percent, andsuitably less than about 1 weight percent, wherein all weight percentsare based on the total weight amount of the poly(lactic acid) polymer;the polybutylene succinate polymer, the polybutylene succinate adipatepolymer, or a mixture of such polymers; and the wetting agent present inthe thermoplastic composition.

The thermoplastic composition used in the present invention is generallythe resulting morphology of a mixture of the poly(lactic acid) polymer;the polybutylene succinate polymer, the polybutylene succinate adipatepolymer, or a mixture of such polymers; the wetting agent, and,optionally, any additional components. In order to achieve the desiredproperties for the thermoplastic composition, it is desirable that thepoly(lactic acid) polymer; the polybutylene succinate polymer, thepolybutylene succinate adipate polymer, or a mixture of such polymers;and the wetting agent remain substantially unreacted with each other. Assuch, each of the poly(lactic acid) polymer; the polybutylene succinatepolymer, the polybutylene succinate adipate polymer, or a mixture ofsuch polymers; and the wetting agent remain distinct components of thethermoplastic composition.

Each of the poly(lactic acid) polymer and the polybutylene succinatepolymer, the polybutylene succinate adipate polymer, or a mixture ofsuch polymers will generally form separate regions or domains within aprepared mixture forming the thermoplastic composition. However,depending on the relative amounts that are used of each of thepoly(lactic acid) polymer and the polybutylene succinate polymer, thepolybutylene succinate adipate polymer, or a mixture of such polymers,an essentially continuous phase may be formed from the polymer that ispresent in the thermoplastic composition in a relatively greater amount.In contrast, the polymer that is present in the thermoplasticcomposition in a relatively lesser amount may form an essentiallydiscontinuous phase, forming separate regions or domains within thecontinuous phase of the more prevalent polymer wherein the moreprevalent polymer continuous phase substantially encases the lessprevalent polymer within its structure. As used herein, the term“encase”, and related terms, are intended to mean that the moreprevalent polymer continuous phase substantially encloses or surroundsthe less prevalent polymer's separate regions or domains.

In one embodiment of a thermoplastic composition or a multicomponentfiber used in the present invention, it is desired that the poly(lacticacid) polymer form an essentially continuous phase and that thepolybutylene succinate polymer, the polybutylene succinate adipatepolymer, or a mixture of such polymers form an essentially discontinuousphase, wherein the poly(lactic acid) polymer substantially encasesregions or domains of the polybutylene succinate polymer, thepolybutylene succinate adipate polymer, or a mixture of such polymers.In such an embodiment, it is desired that the poly(lactic acid) polymeris present in the thermoplastic composition or multicomponent fiber in aweight amount that is between about 75 weight percent to about 90 weightpercent and that the polybutylene succinate polymer, the polybutylenesuccinate adipate polymer, or a mixture of such polymers is present inthe thermoplastic composition or multicomponent fiber in a weight amountthat is between about 5 weight percent to about 20 weight percent,wherein all weight percents are based on the total weight amount of thepoly(lactic acid) polymer, the polybutylene succinate polymer orpolybutylene succinate adipate polymer or a mixture of such polymers,and the wetting agent present in the thermoplastic composition or themulticomponent fiber.

In one embodiment of the present invention, after dry mixing togetherthe poly(lactic acid) polymer; the polybutylene succinate polymer, thepolybutylene succinate adipate polymer, or a mixture of such polymers;and the wetting agent to form a thermoplastic composition dry mixture,such thermoplastic composition dry mixture is beneficially agitated,stirred, or otherwise blended to effectively uniformly mix thepoly(lactic acid) polymer; the polybutylene succinate polymer, thepolybutylene succinate adipate polymer, or a mixture of such polymers;and the wetting agent such that an essentially homogeneous dry mixtureis formed. The dry mixture may then be melt blended in, for example, anextruder, to effectively uniformly mix the poly(lactic acid) polymer;the polybutylene succinate polymer, the polybutylene succinate adipatepolymer, or a mixture of such polymers; and the wetting agent such thatan essentially homogeneous melted mixture is formed. The essentiallyhomogeneous melted mixture may then be cooled and pelletized.Alternatively, the essentially homogeneous melted mixture may be sentdirectly to a spin pack or other equipment for forming fibers or anonwoven structure.

Alternative methods of mixing together the components of the presentinvention include first mixing together the poly(lactic acid) polymerand the polybutylene succinate polymer, the polybutylene succinateadipate polymer, or a mixture of such polymers and then adding thewetting agent to such a mixture in, for example, an extruder being usedto mix the components together. In addition, it is also possible toinitially melt mix all of the components together at the same time.Other methods of mixing together the components of the present inventionare also possible and will be easily recognized by one skilled in theart.

The present invention also utilizes a multicomponent fiber which isprepared from the thermoplastic composition of the present invention.For purposes of illustration only, the present invention will generallybe described in terms of a multicomponent fiber comprising only threecomponents. However, it should be understood that the scope of thepresent invention is meant to include fibers with three or morecomponents.

When the thermoplastic composition is formed into a multicomponentfiber, an exposed surface on at least a portion of the multicomponentfiber will typically be formed from the more prevalent polymer presentin the multicomponent fiber. Such an exposed surface on at least aportion of the multicomponent fiber which will generally permit thermalbonding of the multicomponent fiber to other fibers which may be thesame or different from the multicomponent fiber of the presentinvention. As a result, the multicomponent fiber can then be used toform thermally bonded fibrous nonwoven structures such as a nonwovenweb.

Typical conditions for thermally processing the various componentsinclude using a shear rate that is beneficially between about 100seconds⁻¹ to about 50000 seconds⁻¹, more beneficially between about 500seconds⁻¹ to about 5000 seconds⁻¹, suitably between about 1000 seconds⁻¹to about 3000 seconds⁻¹, and most suitably at about 1000 seconds⁻¹.Typical conditions for thermally processing the components also includeusing a temperature that is beneficially between about 100° C. to about500° C., more beneficially between about 125° C. to about 300° C., andsuitably between about 150° C. to about 250° C.

Methods for making multicomponent fibers are well known and need not bedescribed here in detail. The melt spinning of polymers includes theproduction of continuous filament, such as spunbond or meltblown, andnon-continuous filament, such as staple and short-cut fibers. To form aspunbond or meltblown fiber, generally, a thermoplastic composition isextruded and fed to a distribution system where the thermoplasticcomposition is introduced into a spinneret plate. The spun fiber is thencooled, solidified, and drawn by an aerodynamic system, to be formedinto a conventional nonwoven. Meanwhile, to produce short-cut or staplefiber rather than being directly formed into a nonwoven structure thespun fiber is cooled, solidified, and drawn, generally by a mechanicalrolls system, to an intermediate filament diameter and collected.Subsequently, the fiber may be “cold drawn” at a temperature below itssoftening temperature, to the desired finished fiber diameter andcrimped or texturized and cut into a desirable fiber length.

The process of cooling an extruded thermoplastic composition to ambienttemperature is usually achieved by blowing ambient or sub-ambienttemperature air over the extruded thermoplastic composition. It can bereferred to as quenching or super-cooling because the change intemperature is usually greater than 100° C. and most often greater than150° C. over a relatively short time frame, such as in seconds.

Multicomponent fibers can be cut into relatively short lengths, such asstaple fibers which generally have lengths in the range of about 25 toabout 50 millimeters and short-cut fibers which are even shorter andgenerally have lengths less than about 18 millimeters. See, for example,U.S. Pat. No. 4,789,592 to Taniguchi et al, and U.S. Pat. No. 5,336,552to Strack et al., both of which are incorporated herein by reference intheir entirety.

The resultant multicomponent fibers are desired to exhibit animprovement in hydrophilicity, evidenced by a decrease in the contactangle of water in air. The contact angle of water in air of a fibersample can be measured as either an advancing or a receding contactangle value because of the nature of the testing procedure. Theadvancing contact angle measures a material's initial response to aliquid, such as water. The receding contact angle gives a measure of howa material will perform over the duration of a first insult, or exposureto liquid, as well as over following insults. A lower receding contactangle means that the material is becoming more hydrophilic during theliquid exposure and will generally then be able to transport liquidsmore consistently. Both the advancing and receding contact angle data isdesirably used to establish the highly hydrophilic nature of amulticomponent fiber.

Thus, in one embodiment of the present invention, it is desired that themulticomponent fiber exhibits an Advancing Contact Angle value that isbeneficially less than about 80 degrees, more beneficially less thanabout 75 degrees, suitably less than about 70 degrees, more suitablyless than about 60 degrees, and most suitably less than about 50degrees, wherein the Advancing Contact Angle value is determined by themethod that is described in the Test Methods section herein.

In another embodiment of the present invention, it is desired that themulticomponent fiber exhibits a Receding Contact Angle value that isbeneficially less than about 60 degrees, more beneficially less thanabout 55 degrees, suitably less than about 50 degrees, more suitablyless than about 45 degrees, and most suitably less than about 40degrees, wherein the Receding Contact Angle value is determined by themethod that is described in the Test Methods section herein.

In another embodiment of the present invention, it is desired that thedifference between the Advancing Contact Angle value and the RecedingContact Angle value, commonly known as the contact angle hysteresis, beas small as possible. As such, it is desired that the multicomponentfiber exhibits a difference between the Advancing Contact Angle valueand the Receding Contact Angle value that is beneficially less thanabout 30 degrees, more beneficially less than about 25 degrees, suitablyless than about 20 degrees, and more suitably less than about 10degrees.

Typical poly(lactic acid) polymer materials often undergo heat shrinkageduring downstream thermal processing. The heat-shrinkage mainly occursdue to the thermally-induced chain relaxation of the polymer segments inthe amorphous phase and incomplete crystalline phase. To overcome thisproblem, it is generally desirable to maximize the crystallization ofthe poly(lactic acid) polymer material before the bonding stage so thatthe thermal energy goes directly to melting rather than to allow forchain relaxation and reordering of the incomplete crystalline structure.The typical solution to this problem is to subject the material to aheat-setting treatment. As such, when prepared materials, such asfibers, are subjected to heat-setting upon reaching a bonding roll, thefibers won't substantially shrink because such fibers are already fullyor highly oriented. The present invention alleviates the need for thisadditional processing step because of the morphology of themulticomponent fiber. In general, the addition of the polybutylenesuccinate polymer, the polybutylene succinate adipate polymer, or amixture of such polymers, and the wetting agent decrease the heatshrinkage of a multicomponent fiber as compared to a fiber that isprepared from only poly(lactic acid) polymer.

In one embodiment of the present invention, it is desired that thenonwoven material utilize a thermoplastic composition or amulticomponent fiber which exhibits an amount of shrinking, at atemperature of about 90° C., that is beneficially less than about 15percent, more beneficially less than about 10 percent, and suitably lessthan about 5 percent, wherein the amount of shrinking is based upon thedifference between the initial and final lengths of the fiber divided bythe initial length of the fiber multiplied by 100. The method by whichthe amount of shrinking that a fiber exhibits may be determined isincluded in the Test Methods section herein.

In one embodiment of the present invention, it is desired that themulticomponent fiber exhibit an amount of shrinking, suitably less thanabout 5 percent at a temperature of about 90° C., that results in anonwoven structure formed from the multicomponent fiber to exhibit aquilting or waviness effect that increases the surface area of thenonwoven structure since the shrinking of the multicomponent fiberscauses the nonwoven structure to exhibit a three dimensional topography.Such a quilting or waviness effect of the nonwoven structure has beenfound to improve the softness and z-directional transport of a liquidwithin the nonwoven structure.

It is generally desired that multicomponent fibers also exhibit desiredmechanical strength properties, such as a break stress value as well asa modulus value, such that the nonwoven materials maintain theirintegrity during use. In one embodiment of the present invention, it isdesired that a multicomponent fiber, prepared from the thermoplasticcomposition previously described, exhibits an improved break stressvalue as well as an improved modulus value as compared to a fiber thatis prepared solely from poly(lactic acid) polymer. In one embodiment ofthe present invention, it is desired that the multicomponent fiber alsoexhibits a break stress value that is at least twice the break stressvalue exhibited by an otherwise identical fiber that is prepared solelyfrom the poly(lactic acid) polymer used to prepare the multicomponentfiber.

In one embodiment of the present invention, it is desired that themulticomponent fiber exhibit a break stress value that is greater thanabout 10 MPa, beneficially greater than about 15 MPa, suitably greaterthan about 20 MPa, and up to about 100 MPa.

In another embodiment of the present invention, it is desired that themulticomponent fiber exhibit a modulus value that is less than about 150MPa, beneficially less than about 125 MPa, and suitably less than about100 MPa.

The biodegradable nonwoven materials of the present invention are suitedfor use in disposable products including disposable absorbent productssuch as diapers, adult incontinent products, and bed pads; in catamenialdevices such as sanitary napkins, and tampons; and other absorbentproducts such as wipes, bibs, wound dressings, and surgical capes ordrapes. Accordingly, in another aspect, the present invention relates toa disposable absorbent product comprising the multicomponent fibers.

In one embodiment of the present invention, the multicomponent fibersare formed into a fibrous matrix for incorporation into a disposableabsorbent product. A fibrous matrix may take the form of, for example, afibrous nonwoven web. Fibrous nonwoven webs may be made completely fromthe multicomponent fibers of the present invention or they may beblended with other fibers. The length of the fibers used may depend onthe particular end use contemplated. Where the fibers are to be degradedin water as, for example, in a toilet, it is advantageous if the lengthsare maintained at or below about 15 millimeters.

In one embodiment of the present invention, a disposable absorbentproduct is provided, which disposable absorbent product generallycomprises a composite structure including a liquid-permeable topsheet, afluid acquisition layer, an absorbent structure, and aliquid-impermeable backsheet, wherein at least one of theliquid-permeable topsheet, the fluid acquisition layer, or theliquid-impermeable backsheet comprises the nonwoven material of thepresent invention. In some instances, it may be beneficial for all threeof the topsheet, the fluid acquisition layer, and the backsheet tocomprise the nonwoven material of the present invention.

In another embodiment, the disposable absorbent product may comprisegenerally a composite structure including a liquid-permeable topsheet,an absorbent structure, and a liquid-impermeable backsheet, wherein atleast one of the liquid-permeable topsheet or the liquid-impermeablebacksheet comprises the nonwoven material of the present invention.

In another embodiment of the present invention, the nonwoven materialmay be prepared on a spunbond line. Resin pellets comprising thethermoplastic materials previously described are formed and predried.Then, they are fed to a single extruder. The fibers may be drawn througha fiber draw unit (FDU) or air-drawing unit onto a forming wire andthermally bonded. However, other methods and preparation techniques mayalso be used.

Exemplary disposable absorbent products are generally described in U.S.Pat. Nos. 4,710,187; 4,762,521; 4,770,656; and 4,798,603; whichreferences are incorporated herein by reference.

Absorbent products and structures according to all aspects of thepresent invention are generally subjected, during use, to multipleinsults of a body liquid. Accordingly, the absorbent products andstructures are desirably capable of absorbing multiple insults of bodyliquids in quantities to which the absorbent products and structureswill be exposed during use. The insults are generally separated from oneanother by a period of time.

Test Methods

Melting Temperature

The melting temperature of a material was determined using differentialscanning calorimetry. A differential scanning calorimeter, under thedesignation Thermal Analyst 2910 Differential Scanning Calorimeter,which was outfitted with a liquid nitrogen cooling accessory and used incombination with Thermal Analyst 2200 analysis software (version 8.10)program, both available from T.A. Instruments Inc. of New Castle, Del.,was used for the determination of melting temperatures.

The material samples tested were either in the form of fibers or resinpellets. It was preferred to not handle the material samples directly,but rather to use tweezers and other tools, so as not to introduceanything that would produce erroneous results. The material samples werecut, in the case of fibers, or placed, in the case of resin pellets,into an aluminum pan and weighed to an accuracy of 0.01 mg on ananalytical balance. If needed, a lid was crimped over the materialsample onto the pan.

The differential scanning calorimeter was calibrated using an indiummetal standard and a baseline correction performed, as described in themanual for the differential scanning calorimeter. A material sample wasplaced into the test chamber of the differential scanning calorimeterfor testing and an empty pan is used as a reference. All testing was runwith a 55 cubic centimeter/minute nitrogen (industrial grade) purge onthe test chamber. The heating and cooling program was a 2 cycle testthat begins with equilibration of the chamber to −40° C., followed by aheating cycle of 20° C./minute to 200° C., followed by a cooling cycleat 20° C./minute to −40° C., and then another heating cycle of 20°C./minute to 200° C.

The results were evaluated using the analysis software program whereinthe glass transition temperature (Tg) of inflection, endothermic andexothermic peaks were identified and quantified. The glass transitiontemperature was identified as the area on the line where a distinctchange in slope occurs and then the melting temperature is determinedusing an automatic inflection calculation.

Apparent Viscosity

A capillary under the designation Göttfert Rheograph 2003 capillaryrheometer, which was used in combination with WinRHEO (version 2.31)analysis software, both available from Göttfert Company of Rock Hill,S.C., was used to evaluate the apparent viscosity rheological propertiesof material samples. The capillary rheometer setup included a 2000 barpressure transducer and a 30 mm length/30 mm active length/1 mmdiameter/0 mm height/180° run in angle, round hole capillary die.

If the material sample being tested demonstrated or was known to havewater sensitivity, the material sample was dried in a vacuum oven aboveits glass transition temperature, i.e. above 55 or 60° C. forpoly(lactic acid) materials, under a vacuum of at least 15 inches ofmercury with a nitrogen gas purge of at least 30 standard cubic feet perhour for at least 16 hours.

Once the instrument was warmed up and the pressure transducer wascalibrated, the material sample was loaded incrementally into thecolumn, packing resin into the column with a ramrod each time to ensurea consistent melt during testing. After material sample loading, a 2minute melt time preceded each test to allow the material sample tocompletely melt at the test temperature. The capillary rheometer tookdata points automatically and determined the apparent viscosity (inPascal·second) at 7 apparent shear rates (in seconds⁻¹): 50, 100, 200,500, 1000, 2000, and 5000. When examining the resultant curve it wasimportant that the curve be relatively smooth. If there were significantdeviations from a general curve from one point to another, possibly dueto air in the column, the test run was repeated to confirm the results.

The resultant rheology curve of apparent shear rate versus apparentviscosity gives an indication of how the material sample will run atthat temperature in an extrusion process. The apparent viscosity valuesat a shear rate of at least 1000 seconds⁻¹ are of specific interestbecause these are the typical conditions found in commercial fiberspinning extruders.

Molecular Weight

A gas permeation chromatography (GPC) method was used to determine themolecular weight distribution of samples, such as of poly(lactic acid)whose weight average molecular weight (M_(w)) is between about 800 toabout 400,000.

The GPC was set up with two PL gel Mixed K linear 5 micron, 7.5×300millimeter analytical columns in series. The column and detectortemperatures were 30° C. The mobile phase was high-performance liquidchromatography (HPLC) grade tetrahydrofuran (THF). The pump rate was 0.8milliliter per minute with an injection volume of 25 microliters. Totalrun time was 30 minutes. It is important to note that new analyticalcolumns must be installed about every 4 months, a new guard column aboutevery month, and a new in-line filter about every month.

Standards of polystyrene polymers, obtained from Aldrich Chemical Co.,were mixed into a solvent of dichloromethane(DCM):THF (10:90), both HPLCgrade, to obtain 1 mg/mL concentrations. Multiple polystyrene standardscould be combined in one standard solution provided that their peaks donot overlap when chromatographed. A range of standards of about 687 to400,000 molecular weight were prepared. Examples of standard mixtureswith Aldrich polystyrenes of varying weight average molecular weightsinclude: Standard 1 (401,340; 32,660; 2,727), Standard 2 (45,730;4,075), Standard 3 (95,800; 12,860) and Standard 4 (184,200; 24,150;687).

Next, the stock check standard was prepared. First, 10 g of a 200,000molecular weight poly(lactic acid) standard, Catalog #19245 obtainedfrom Polysciences Inc., was dissolved to 100 ml of HPLC grade DCM in aglass jar with a lined lid using an orbital shaker (at least 30minutes). Next. the mixture was poured out onto a clean, dry, glassplate and the solvent allowed to evaporate, then placed in a 35° C.preheated vacuum oven and dried for about 14 hours under a vacuum of 25mm of mercury. Next, the poly(lactic acid) was removed from the oven andthe film cut into small strips. Immediately, the samples were groundusing a grinding mill (with a 10 mesh screen) taking care not to add toomuch sample and causing the grinder to freeze up. A few grams of theground sample were stored in a dry glass jar in a dessicator, while theremainder of the sample can be stored in the freezer in a similar typejar.

It was important to prepare a new check standard prior to the beginningof each new sequence and, because the molecular weight is greatlyaffected by sample concentration, great care should be taken in itsweighing and preparation. To prepare the check standard, 0.0800 g±0.0025g of 200,000 weight average molecular weight poly(lactic acid) referencestandard was weighed out into a clean dry scintillation vial. Then,using a volumetric pipette or dedicated repipet, 2 ml of DCM was addedto the vial and the cap screwed on tightly. The sample was allowed todissolve completely. The sample was swirled on an orbital shaker, suchas a Thermolyne Roto Mix (type 51300) or similar mixer, if necessary. Toevaluate whether was it dissolved, the vial was held up to the light ata 45° angle. The vial was turned slowly and the liquid watched as itflowed down the glass. If the bottom of the vial did not appear smooth,the sample was not completely dissolved. It may take the sample severalhours to dissolve. Once dissolved, 18 ml of THF was added using avolumetric pipette or dedicated repipet, the vial capped tightly andmix.

Sample preparations began by weighing 0.0800 g ±0.0025 g of the sampleinto a clean, dry scintillation vial (great care should also be taken inits weighing and preparation). 2 ml of DCM was added to the vial with avolumetric pipette or dedicated repipette and the cap screwed ontightly. The sample was allowed to dissolve completely using the sametechnique described in the check standard preparation above. Then 18 mlof THF was added using a volumetric pipette or dedicated repipette, thevial capped tightly and mixed.

The evaluation was begun by making a test injection of a standardpreparation to test the system equilibration. Once equilibration wasconfirmed the standard preparations were injected. After those were run,first the check standard preparation was injected and then the samplepreparations. The check standard preparation was injected after every 7sample injections and at the end of testing. Be careful not to take anymore than two injections from any one vial, and those two injectionsmust be made within 4.5 hours of each other.

There are 4 quality control parameters to assess the results. First, thecorrelation coefficient of the fourth order regression calculated foreach standard should be not less than 0.950 and not more than 1.050.Second, the relative standard deviation of all the weight averagemolecular weights of the check standard preparations should not be morethan 5.0 percent. Third, the average of the weight average molecularweights of the check standard preparation injections should be within 10percent of the weight average molecular weight on the first checkstandard preparation injection. Lastly, record the lactide response forthe 200 microgram per milliliter (μg/mL) standard injection on a SQCdata chart. Using the chart's control lines, the response must be withinthe defined SQC parameters.

Calculate the Molecular statistics based on the calibration curvegenerated from the polystyrene standard preparations and constants forpoly(lactic acid) and polystyrene in THF at 30° C. Those are:Polystyrene (K=14.1*10⁵, alpha=0.700) and poly(lactic acid) (K=54.9*10⁵,alpha=0.639).

Heat Shrinkage of Fibers

The required equipment for the determination of heat shrinkage include:a convection oven (Thelco model 160DM laboratory oven, available fromPrecision and Scientific Inc., of Chicago, Ill.), 0.5 g (+/−0.06 g)sinker weights, 1 inch binder clips, masking tape, graph paper with atleast 1 inch squares, foam posterboard (11 by 14 inches) or equivalentsubstrate to attach the graph paper and samples to. The convection ovenshould be capable of a temperature of about 100° C.

Fiber samples are melt spun at their respective spinning conditions. Ingeneral, a 30 filament bundle is preferred and mechanically drawn toobtain fibers with a jetstretch ratio of beneficially 224 or higher.Only fibers of the same jetstretch ratio can be compared to one anotherin regards to their heat shrinkage. The jetstretch ratio of a fiber isthe ratio of the speed of the drawdown roll divided by the linearextrusion rate (distance/time) of the melted polymer exiting thespinneret. The spun fiber is usually collected onto a bobbin using awinder. The collected fiber bundle was separated into 30 filaments, if a30 filament bundle has not already been obtained, and cut into 9 inchlengths.

The graph paper was taped onto the posterboard where one edge of thegraph paper was matched with the edge of the posterboard. One end of thefiber bundle was taped, no more than the end 1 inch. The taped end wasclipped to the posterboard at the edge where the graph paper was matchedup such that the edge of the clip rests over one of the horizontal lineson the graph paper while holding the fiber bundle in place (the tapedend should be barely visible as it is secured under the clip). The otherend of the bundle was pulled taught and lined up parallel to thevertical lines on the graph paper. Next, at 7 inches down from the pointwhere the clip is binding the fiber, the 0.5 g sinker was pinched aroundthe fiber bundle. The attachment process was repeated for eachreplicate. Usually, 3 replicates could be attached at one time. Markscould be made on the graph paper to indicate the initial positions ofthe sinkers. The samples were placed into the oven at a temperature ofabout 100° C. such that the samples hung vertically and did not touchthe posterboard. At time intervals of 5, 10 and 15 minutes quickly thenew location of the sinkers was marked on the graph paper and samplesreturned to the oven.

After the testing was complete, the posterboard was removed and thedistances between the origin (where the clip held the fibers) and themarks at 5, 10 and 15 minutes were measured with a ruler graduated to{fraction (1/16)} inch. Three replicates per sample is recommended.Calculate averages, standard deviations and percent shrinkage. Thepercent shrinkage is calculated as (initial length—measured length)divided by the initial length and multiplied by 100. As reported in theexamples herein and as used throughout the claims, the Heat Shrinkagevalue represents the amount of heat shrinkage that a fiber sampleexhibits at a temperature of about 100° C. for a time period of about 15minutes, as determined according to the preceding test method.

Contact Angle

The equipment includes a DCA-322 Dynamic Contact Angle Analyzer andWinDCA (version 1.02) software, both available from ATI-CAHNInstruments, Inc., of Madison, Wis. Testing was done on the “A” loopwith a balance stirrup attached. Calibrations should be done monthly onthe motor and daily on the balance (100 mg mass used) as indicated inthe manual.

Thermoplastic compositions were spun into fibers and the freefall sample(jetstretch of 0) was used for the determination of contact angle. Careshould be taken throughout fiber preparation to minimize fiber exposureto handling to ensure that contamination is kept to a minimum. The fibersample was attached to the wire hanger with scotch tape such that 2-3 cmof fiber extended beyond the end of the hanger. Then the fiber samplewas cut with a razor so that approximately 1.5 cm was extending beyondthe end of the hanger. An optical microscope was used to determine theaverage diameter (3 to 4 measurements) along the fiber.

The sample on the wire hanger was suspended from the balance stirrup onloop “A”. The immersion liquid was distilled water and it was changedfor each specimen. The specimen parameters were entered (i.e. fiberdiameter) and the test started. The stage advanced at 151.75microns/second until it detected the Zero Depth of Immersion when thefiber contacted the surface of the distilled water. From the Zero Depthof Immersion, the fiber advanced into the water for 1 cm, dwelled for 0seconds and then immediately receded 1 cm. The auto-analysis of thecontact angle done by the software determined the advancing and recedingcontact angles of the fiber sample based on standard calculationsidentified in the manual. Contact angles of 0 or <0 indicate that thesample had become totally wettable. Five replicates for each sample weretested and a statistical analysis for mean, standard deviation, andcoefficient of variation percent was calculated. As reported in theexamples herein and as used throughout the claims, the Advancing ContactAngle value represents the advancing contact angle of distilled water ona fiber sample determined according to the preceding test method.Similarly, as reported in the examples herein and as used throughout theclaims, the Receding Contact Angle value represents the receding contactangle of distilled water on a fiber sample determined according to thepreceding test method.

Fluid-Intake and Flowback Evaluation (FIFE)

Fluid-Intake and Flowback Evaluation (FIFE) testing was used todetermine the absorbency time and flowback of a personal care product. AMaster-Flex Digi-Staltic Automatic Dispensing system was supplied withsaline colored with a small amount of FD&C blue dye, set to provide 80mL insults, and dispensed several times to eliminate any air bubbles.The product samples, infant care diapers, were prepared without elasticsso that they would easily lie flat. Two 3.5 inch by 12 inch blotterpaper samples were weighed. These papers were placed on the FIFE board,a simple board with a 3 inch by 6 inch raised platform in the middle.The blotter papers were aligned so that they ran lengthwise along eitherside of the raised platform. The diaper was then aligned so that thearea to be insulted was carefully centered on the raised platform, withthe topsheet facing up, such that there were no visible wrinkles in thenonwoven topsheet. The second FIFE board was then placed on top of theproduct. This apparatus consists of a flat board that was intersected bya hollow cylinder, protruding only from the top side of the board. Thecircular region created where the cylinder intersected the flat plane ofthe board was hollow. The inner diameter of the cylinder was 5.1centimeters. A funnel with an inner diameter of 7 millimeters at theshort end was placed in the cylinder. The fluid was then dispensed bythe pump directly into the funnel. The intake time was recorded bystopwatch from the time the fluid hit the funnel to the moment no fluidwas visible on the specimen surface. The blotter papers were checked forproduct leakage and if any occurred the weight of the blotter paperswould have been measured to determine the quantity of fluid that leaked.In the described testing, no leakage occurred. Approximately one minuteelapsed before the second insult was applied in the same manner. Again athird insult was applied and timed in the same manner. If desired aprocedure may then follow to determine the amount of fluid flowing backwhen the product is under pressure. In this case, only the intake rateswere recorded.

TransEpidermal Water Loss (TEWL)

TransEpidermal Water Loss (TEWL) armband testing was used to measurechanges in skin hydration as a result of product use. A lowerevaporation value, as measured by a Servo Med Evaporimeter, isindicative of a product that promotes skindryness. This test actuallyreports a difference in evaporation values. A measurement of moistureevaporation rate is taken prior to the test and then immediatelyfollowing. The difference in these numbers provides the TEWL value asreported in the results. A lower TEWL value implies that a productprovides better breathability to the skin.

Product, in this case infant care diapers, was prepared by hand withoutany elastics or ears. The basic structure of the diaper was the same,but one control diaper consisted entirely of standard materials and theother had all standard materials except for the topsheet, which wascomprised of the biodegradable nonwoven. The target area for the insultswas drawn in permanent marker on the outside of the product. All testingoccurred in a controlled environment of 72±4 F. with a relative humidityof 40±5%. The subjects were adult women who were carefully selected toinsure that they had no conditions that might potentially alter theresults of such a test.

Subjects relaxed in a controlled environment until a stable baselinereading of less than 10 g²/m/hr is obtained with the Servo MedEvaporimeter. These measurements were performed on the inner forearm ofthe subjects. Masterflex Digi-Staltic batch/dispense pump was used withsilicone tubing in the pump head, which was connected to neoprene tubingfor dispensing, by barb fittings. The end of the neoprene dispensingtube was placed on the forearm of a subject and the product applied tothe forearm with the target insult area directly on top of the tubeopening. The product is secured with tape that was wrapped around thediaper and did not contact the skin. The diaper was then loaded withthree insults of 60 mL of saline at 45 second intervals and the tuberemoved. The product was further secured with a stretchable net and thesubject required to sit for one hour. After 60 minutes of wear, theproduct was removed and the Evaporimeter was then used to obtainreadings every second for two minutes in the same area on the forearm asthe baseline readings were taken. The reported result is the differencebetween the one-hour and baseline readings.

EXAMPLES

Various materials were used as components to form thermoplasticcompositions and multicomponent fibers in the following Examples. Thedesignation and various properties of these materials are listed inTable 1.

Heplon A10005 poly(lactic acid) (PLA) polymers were obtained fromChronopol Inc., Golden, Colo.

A polybutylene succinate (PBS), available from Showa Highpolymer Co.,Ltd., Tokyo, Japan, under the designation Bionolle 1020 polybutylenesuccinate, was obtained.

A polybutylene succinate (PBS) with long chain branching, available fromShowa Highpolymer Co., Ltd., Tokyo, Japan, under the designationBionolle 1903 polybutylene succinate, was obtained.

The wetting agent used throughout the examples was obtained fromPetrolite Corporation of Tulsa, Okla., under the designation UNITHOX®480ethoxylated alcohol, which exhibited a number average molecular weightof about 2250, an ethoxylate percent of about 80 weight percent, and anHLB value of about 16.

TABLE 1 Weight Number Residual Material Melting Average Average Polydis-Lactic Designa- L:D Temp. Molecular Molecular persity Acid tion Ratio (°C.) Weight Weight Index Monomer PLA 100:0 175 187,000 118,000 1.58 <1%Sample 1 PLA 95:5 140- 190,000 108,000 1.76 <3% Sample 2 145 BionolleN/A 95 40,000 to 20,000 to ˜2 to N/A 1020 1,000,000 300,000 ˜3.3Bionolle N/A 120 40,000 to 20,000 to ˜2 to N/A 1903 1,000,000 300,000˜3.3

Examples 1-5

Thermoplastic compositions were prepared using varying amounts of apoly(lactic acid) polymer, a polybutylene succinate, and a wettingagent. To prepare a specific thermoplastic composition, the variouscomponents were first dry mixed and then melt blended in acounter-rotating twin screw to provide vigorous mixing of thecomponents. The melt mixing involves partial or complete melting of thecomponents combined with the shearing effect of rotating mixing screws.Such conditions are conducive to optimal blending and even dispersion ofthe components of the thermoplastic composition. Twin screw extruderssuch as a Haake Rheocord 90, available from Haake GmbH of Karlsautte,Germany, or a Brabender twin screw mixer (cat no 05-96-000) availablefrom Brabender Instruments of South Hackensack, N.J., or othercomparable twin screw extruders, are well suited to this task. Themelted composition is cooled following extrusion from the melt mixer byforced air passed over the extrudate. The cooled composition is thensubsequently pelletized for conversion to fibers.

Converting these resins into fibers was conducted on a in-house 0.75inch diameter extruder with a 24:1 L:D (length:diameter) ratio screw andthree heating zones which feed into a transfer pipe from the extruder tothe spin pack, which constitutes the 4th heating zone and contains a0.62 inch diameter Koch® SMX type static mixer unit, available from KochEngineering Company Inc. of New York, N.Y., and then into the spinninghead (5th heating zone) and through a spin plate which is simply a platewith numerous small holes through which the molten polymer will beextruded through. The spin plate used herein had 15 to 30 holes, whereeach hole has a 20 mil diameter. The fibers were air quenched using airat a temperature range of 13° C. to 22° C., and drawn down by amechanical draw roll and passed on to either a winder unit forcollection, or to a fiber drawing unit for spunbond formation andbonding, or through accessory equipment for heat setting or othertreatment before collection.

The polymers were converted to a spunbond nonwoven material and wereperformed using 14″ and 20″ fiber spinning lines. A monocomponent fiberwas produced from a single extruder and the fibers were drawn and laidthrough a fiber draw unit (FDU). The webs were then thermally bondedinline with a wire-weave bond pattern.

The wettability of the nonwoven material Examples was quantified throughthe use of contact angle measurement, wherein a lower contact angle isindicative of a more wettable material. Contact angle measurements wereperformed on the Cahn DCA-322 Dynamic Contact Angle Analyzer using theWinDCA version 1.02 analysis software. Resins were spun into freefallfibers to be used in this measurement. Extensive care was taken that thesamples were not handled extensively to help prevent contamination. Asingle fiber approximately 3 cm long was attached to a thin wire hangerwith tape such that 1.5 cm of the fiber extended beyond the end of thehanger. The fiber diameter was measured with the use of an opticalmicroscope and entered into the computer. Other parameters such as fibershape and surface tension of the liquid to be used were also enteredinto the software. For these Examples, distilled water was used as theliquid.

The fiber was hung from the “A” loop balance and a small beaker of waterwas placed beneath it so that the end of the fiber was almost touchingthe surface of the liquid. The stage holding the fiber advanced at151.75 microns/second until it detected the Zero Depth of Immersion(ZDOI) when the fiber contacted the surface of the distilled water. Fromthe ZDOI, it advanced 1 cm, dwelled for 0 seconds, then immediatelyreceded 1 cm. The data analysis was performed automatically by theanalysis software. Each sample was tested five times and the averagevalues were calculated for both advancing and receding contact angles.

The results for advancing and receding contact angles are given in Table2. The advancing contact angle is a measure of how a material willinteract with fluid during its first contact with liquid. The recedingcontact angle is an indication of how the material will behave duringmultiple insults with liquid or in a damp, high humidity environment.The blends included in this invention produced highly wettable fibers.

TABLE 2 Contact Angle Data Advancing Contact Material Angle RecedingContact Angle PLA:PBS:Unithox 71 44 (78:9:13) PLA:PBS:Unithox 73 44(86:9:5) PLA:PBS:Unithox 77 49 (87:10:3) PLA:PBS:Unithox 79 55 (89:10:1)Polypropylene 128 94

Table 3 gives the results for the fluid management properties of thenonwoven materials of the present invention. As the table demonstrates,the nonwoven materials of the present invention have a much fasterintake time than the control surfactant-treated polypropylene spunbondliner. With subsequent insults, the surfactant begins to wash off thetreated diaper liner and the intake times rise significantly. Thepermanently hydrophilic surface of the nonwoven material of the presentinvention remains permanently wettable, so that while intake timesincrease, they remain much lower than those for the polypropylene liner.In addition, the liner made using the nonwoven material of the presentinvention also demonstrates a lower Flowback than the control liner.This low flowback is significant because it indicates that underpressure, very little fluid will flow back to the user side of theliner, keeping skin drier.

One of the most significant tests for skin dryness is how the materialbehaves in a TEWL test, which measures skin dryness when covered with adiaper insulted with saline. The lower TEWL value demonstrated by thenonwoven material of the present invention indicates an improvement inskin dryness.

TABLE 3 Fluid Management Properties Control-0.5 osy 0.8 osypolypropylene PLA:PBU:Unithox spunbond blend FIFE - 1^(st) Insult Time28.03 22.68 (sec) FIFE - 2^(nd) Insult Time 83.03 54.08 (sec) FIFE -3^(rd) Insult Time 94.98 55.95 (sec) Flowback (grams) 3.40 1.99 TEWL(g/m²) 22.1 19.1

Those skilled in the art will recognize that the present invention iscapable of many modifications and variations without departing from thescope thereof. Accordingly, the detailed description and examples setforth above are meant to be illustrative only and are not intended tolimit, in any manner, the scope of the invention as set forth in theappended claims.

What is claimed is:
 1. A biodegradable nonwoven material comprising aplurality of fibers of a thermoplastic composition, wherein thethermoplastic composition comprises: a. a poly(lactic acid) polymer in aweight amount that is greater than 0 but less than 100 weight percent;b. a polymer selected from the group consisting of a polybutylenesuccinate polymer, a polybutylene succinate adipate polymer, and amixture of such polymers, in a weight amount that is greater than 0 butless than 100 weight percent; and c. a wetting agent, which exhibits ahydrophilic-lipophilic balance ratio that is between about 10 to about40, in a weight amount that is greater than 0 to about 15 weightpercent, wherein all weight percents are based on the total weightamount of the poly(lactic acid) polymer; the polymer selected from thegroup consisting of a polybutylene succinate polymer, a polybutylenesuccinate adipate polymer, and a mixture of such polymers; and thewetting agent present in the thermoplastic composition.
 2. Thebiodegradable nonwoven material of claim 1, wherein the poly(lacticacid) polymer is present in a weight amount that is between about 5weight percent to about 95 weight percent, the polymer selected from thegroup consisting of a polybutylene succinate polymer, a polybutylenesuccinate adipate polymer, and a mixture of such polymers, is present ina weight amount that is between about 5 weight percent to about 95weight percent, and the wetting agent is present in a weight amount thatis between about 0.5 weight percent to about 15 weight percent.
 3. Thebiodegradable nonwoven material of claim 2, wherein the poly(lacticacid) polymer is present in a weight amount that is between about 10weight percent to about 90 weight percent, the polymer selected from thegroup consisting of a polybutylene succinate polymer, a polybutylenesuccinate adipate polymer, and a mixture of such polymers, is present ina weight amount that is between about 10 weight percent to about 90weight percent, and the wetting agent is present in a weight amount thatis between about 1 weight percent to about 13 weight percent.
 4. Thebiodegradable nonwoven material of claim 1, wherein the wetting agentexhibits a hydrophilic-lipophilic balance ratio that is between about 10to about
 20. 5. The biodegradable nonwoven material of claim 1, whereinthe wetting agent is an ethoxylated alcohol.
 6. The biodegradablenonwoven material of claim 1, wherein the poly(lactic acid) polymer ispresent in a weight amount that is between about 75 weight percent toabout 90 weight percent and the polymer selected from the groupconsisting of a polybutylene succinate polymer, a polybutylene succinateadipate polymer, and a mixture of such polymers, is present in a weightamount that is between about 5 weight percent to about 20 weightpercent, and the wetting agent is an ethoxylated alcohol.
 7. Abiodegradable nonwoven material comprising a plurality of multicomponentfibers, wherein the multicomponent fibers are prepared from athermoplastic composition, wherein the thermoplastic compositioncomprises: a. a poly(lactic acid) polymer in a weight amount that isgreater than 0 but less than 100 weight percent; b. a polymer selectedfrom the group consisting of a polybutylene succinate polymer, apolybutylene succinate adipate polymer, and a mixture of such polymers,in a weight amount that is greater than 0 but less than 100 weightpercent; and c. a wetting agent, which exhibits a hydrophilic-lipophilicbalance ratio that is between about 10 to about 40, in a weight amountthat is greater than 0 to about 15 weight percent, wherein all weightpercents are based on the total weight amount of the poly(lactic acid)polymer; the polymer selected from the group consisting of apolybutylene succinate polymer, a polybutylene succinate adipatepolymer, and a mixture of such polymers; and the wetting agent presentin the thermoplastic composition; further wherein the multicomponentfiber exhibits an Advancing Contact Angle value that is less than about80 degrees and a Receding Contact Angle value that is less than about 60degrees.
 8. The biodegradable nonwoven material of claim 7, wherein thepoly(lactic acid) polymer is present in a weight amount that is betweenabout 5 weight percent to about 95 weight percent, the polymer selectedfrom the group consisting of a polybutylene succinate polymer, apolybutylene succinate adipate polymer, and a mixture of such polymers,is present in a weight amount that is between about 5 weight percent toabout 95 weight percent, and the wetting agent is present in a weightamount that is between about 0.5 weight percent to about 15 weightpercent.
 9. The biodegradable nonwoven material of claim 7, wherein thewetting agent exhibits a hydrophilic-lipophilic balance ratio that isbetween about 10 to about
 20. 10. The biodegradable nonwoven material ofclaim 7, wherein the wetting agent is an ethoxylated alcohol.
 11. Thebiodegradable nonwoven material of claim 7, wherein the multicomponentfiber exhibits an Advancing Contact Angle value that is less than about75 degrees and a Receding Contact Angle value that is less than about 55degrees.
 12. The biodegradable nonwoven material of claim 11, whereinthe difference between the Advancing Contact Angle value the RecedingContact Angle value is less than about 30 degrees.
 13. The biodegradablenonwoven material of claim 7, wherein the multicomponent fiber exhibitsa Heat Shrinkage value that is less than about 15 percent.
 14. Thebiodegradable nonwoven material of claim 7, wherein the poly(lacticacid) polymer is present in a weight amount that is between about 75weight percent to about 90 weight percent, the polymer selected from thegroup consisting of a polybutylene succinate polymer, a polybutylenesuccinate adipate polymer, and a mixture of such polymers, is present ina weight amount that is between about 5 weight percent to about 20weight percent, the wetting agent is an ethoxylated alcohol, thedifference between an Advancing Contact Angle value and a RecedingContact Angle value is less than about 30 degrees, and themulticomponent fiber exhibits a Heat Shrinkage value that is less thanabout 15 percent.
 15. A biodegradable nonwoven material comprising aplurality of multicomponent fibers, wherein the multicomponent fibersare prepared from a plurality of components, further wherein one of thecomponents comprises an unreacted thermoplastic mixture comprising: a. apoly(lactic acid) polymer in a weight amount that is greater than 0 butless than 100 weight percent; b. a polymer selected from the groupconsisting of a polybutylene succinate polymer, a polybutylene succinateadipate polymer, and a mixture of such polymers, in a weight amount thatis greater than 0 but less than 100 weight percent; and c. a wettingagent, which exhibits a hydrophilic-lipophilic balance ratio that isbetween about 10 to about 40, in a weight amount that is greater than 0to about 15 weight percent, wherein all weight percents are based on thetotal weight amount of the poly(lactic acid) polymer; the polymerselected from the group consisting of a polybutylene succinate polymer,a polybutylene succinate adipate polymer, and a mixture of suchpolymers; and the wetting agent present in the thermoplasticcomposition; further wherein the plurality of multicomponent fibers arearranged in a configuration such that the unreacted thermoplasticcomponent is located at a surface of the multicomponent fiber.
 16. Thebiodegradable nonwoven material of claim 15, wherein the poly(lacticacid) polymer is present in a weight amount that is between about 5weight percent to about 95 weight percent, the polymer selected from thegroup consisting of a polybutylene succinate polymer, a polybutylenesuccinate adipate polymer, and a mixture of such polymers, is present ina weight amount that is between about 5 weight percent to about 95weight percent, and the wetting agent is present in a weight amount thatis between about 0.5 weight percent to about 15 weight percent.
 17. Thebiodegradable nonwoven material of claim 15, wherein the wetting agentexhibits a hydrophilic-lipophilic balance ratio that is between about 10to about
 20. 18. The biodegradable nonwoven material of claim 15,wherein the wetting agent is an ethoxylated alcohol.
 19. Thebiodegradable nonwoven material of claim 15, wherein the multicomponentfiber exhibits an Advancing Contact Angle value that is less than about75 degrees and a Receding Contact Angle value that is less than about 55degrees.
 20. The biodegradable nonwoven material of claim 19, whereinthe difference between the Advancing Contact Angle value the RecedingContact Angle value is less than about 30 degrees.
 21. The biodegradablenonwoven material of claim 15, wherein the multicomponent fiber exhibitsa Heat Shrinkage value that is less than about 15 percent.
 22. Thebiodegradable nonwoven material of claim 15, wherein the poly(lacticacid) polymer is present in a weight amount that is between about 75weight percent to about 90 weight percent, the polymer selected from thegroup consisting of a polybutylene succinate polymer, a polybutylenesuccinate adipate polymer, and a mixture of such polymers, is present ina weight amount that is between about 5 weight percent to about 20weight percent, the wetting agent is an ethoxylated alcohol, thedifference between an Advancing Contact Angle value and a RecedingContact Angle value is less than about 30 degrees, and themulticomponent fiber exhibits a Heat Shrinkage value that is less thanabout 15 percent.
 23. A biodegradable nonwoven material comprising aplurality of multicomponent fibers, wherein the multicomponent fibersexhibit an Advancing Contact Angle value that is less than about 80degrees and a Receding Contact Angle value that is less than about 60degrees.